1. Field of the Invention
The present invention relates to a method and apparatus for automatic correction of a direct exposure apparatus comprising a plurality of exposure heads that have exposure elements arranged in a two-dimensional manner at an inclination with respect to relative movement of an exposure target and that are arranged in a direction orthogonal to the relative movement.
2. Description of the Related Art
In recent years, patterning methods, by direct exposure, that do not use photomasks have been proposed. According to these methods, correction for dealing with expansion and contraction, distortion, deviation and the like of substrates can be performed easily at the stage of generation of exposure data in advance or in real time and, therefore, in comparison with patterning methods using photomasks that have been commonly used in the past, remarkable improvement such as increased manufacturing accuracy and yield, shorter delivery time, reduced manufacturing costs and the like can be achieved.
The patterning methods by direct exposure include, for example, methods for forming exposure patterns by direct exposure process using a Digital Micromirror Device (DMD) or an electron beam exposure machine.
Japanese Unexamined Patent Publication No. 10-112579 describes an example of the conventional patterning methods by direct exposure using DMD. In this technique, when a resist formed on an exposure target (e.g., an exposure target substrate) is exposed directly, pattern data is generated according to a pattern to be exposed, then, this pattern data is input to Digital Micromirror Device (DMD) and, then, a plurality of micro mirrors of the DMD are tilted according to the pattern data so that directions of reflected light from each micro mirror obtained by projecting light on the DMD are changed appropriately and the reflected light illuminates the resist on the exposure target substrate. As a result of this illumination, an exposure pattern corresponding to the pattern data is formed. In general, the micro mirrors in the DMD are arranged in a two-dimensional manner so that directions in which rows and columns are arranged intersect each other at right angles. Therefore, the distance between the micro mirrors would usually correspond to resolution of the wiring pattern that can be formed by the direct exposure apparatus.
Further, National Publication of Translated Version No. 2001-521672 (corresponding to WO98/47042) discloses a technique in which micro mirrors arranged in a two-dimensional manner are tilted with respect to a direction of relative movement of an exposure target substrate so that direct exposure process can be performed with resolution smaller than the space between the micro mirrors of a DMD. Still further, Japanese Unexamined Patent Publication No. 2004-226520 discloses a technique for adjusting the tilt angles of the micro mirrors of a DMD.
FIG. 16 is a diagram schematically showing a direct exposure system. A direct exposure system 100 comprises a direct exposure apparatus 101, and a computing machine 102 connected to the direct exposure apparatus 101. The computing machine 102 supplies exposure data to the direct exposure apparatus 101 and controls the direct exposure apparatus 101. The direct exposure apparatus 101 comprises a stage 110 on which an exposure target substrate 151 is mounted, and exposure means 111 that moves above the exposure target substrate 151 with respect thereto in the direction of the arrow in the figure. The exposure means 111 comprises a plurality of exposure heads (not shown) to which an area to be exposed on a surface of the exposure target substrate 151 is assigned and each of which performs exposure process in parallel. When the direct exposure apparatus comprises a DMD, exposure elements in the exposure heads are the micro mirrors of the DMD.
FIG. 17 is a diagram exemplifying exposure heads in a conventional direct exposure apparatus. In the figure, micro mirrors of a DMD constituting exposure heads 200-A, 200-B and 200-C are designated by circles (a reference symbol Q). Here, it is to be noted that the number and size of the exposure heads 200-A, 200-B and 200-C and the micro mirrors Q arranged thereon in a two-dimensional manner is shown merely by way of example. Typically, one exposure head cannot expose an entire area of the exposure target substrate and, therefore, a plurality of exposure heads 200-A, 200-B and 200-C are arranged in a direction orthogonal to relative movement of the exposure target substrate and used for exposure process.
An area on a line along the relative movement of the exposure target substrate is illuminated by a plurality of exposure elements. More specifically, as shown in FIG. 17, for example, five exposure elements (indicated by black-filled circles in the figure) get involved in the exposure process on a line α and four exposure elements (also indicated by black-filled circles in the figure) get involved in the exposure process on a line β.
As described above, in the direct exposure apparatus, whether the intended exposure process is completed or not is determined by whether the light energy accumulated through k exposures exceeds the threshold for exposing the photoresist applied on the exposure target substrate. Therefore, if a sufficient number of exposure elements are provided, for example, some exposure elements may not illuminate normally due to failure of micro mirrors in DMD in a DMD-based patterning method, driving transistors of LCD elements and the like, but the eventual exposure result is not likely to be seriously affected. In other words, reliability of the direct exposure apparatus is based on redundancy of the number of exposure elements described above.
However, attachment positions of adjacent exposure heads may deviate due to some reasons such as mechanical errors and the like. For example, as shown in FIG. 17, when the attachment position of the exposure head 100-B constituted by the DMD deviates from that of the adjacent exposure head 100-C, only two exposure elements (indicated by black-filled circles in the figure) get involved in the exposure process on a line γ, while two exposure elements that are indicated by diagonally shaded circles in the figure and that should get involved in the exposure process essentially fall outside the line γ. When there are deviations of the attachment positions of the exposure heads as described above, the decreased number of exposure elements getting involved in the exposure process cannot ensure sufficient light energy required for exposure and, as a result, wiring patterns of finished products may be affected seriously.
In order to correct the deviations of the attachment positions of the exposure heads as described above, in the past, an image of wiring patterns obtained by actual direct exposure in the concerned direct exposure apparatus is observed by using a microscope to measure actual deviations. Such procedure is time and labor consuming and it takes unwanted costs to expose a substrate and form wirings actually.
Thus, in view of the above problem, it is an object of the present invention to provide a method and apparatus for automatic correction that obtains correction amounts for correcting deviations of attachment positions of exposure heads in a direct exposure apparatus comprising a plurality of exposure heads that have exposure elements arranged in a two-dimensional manner with an inclination with respect to relative movement of an exposure target and that are arranged in a direction orthogonal to the relative movement.